1. Field of the Invention
The present invention relates to an apparatus for tightening connecting rod attachment members for fastening bolts or nuts as the attachment members in order to attach a connecting rod to a crankshaft.
2. Description of the Related Art
A multi-spindle nut runner apparatus, which is disclosed, for example, in Japanese Laid-Open Utility Model Publication No. 63-21531, has been hitherto used when a connecting rod is fastened with bolts or nuts to a crankshaft for constructing an engine. Such a multi-spindle nut runner apparatus is operated as follows in order to join the connecting rod by being fastened with nuts with respect to a plurality of pin sections of the crankshaft. That is, a nut runner socket corresponding to the pin sections disposed on a side of the top dead center of the crankshaft is allowed to make abutment prior to a nut runner socket corresponding to the pin sections disposed on the bottom dead center. The force of abutment, which is exerted by the nut runner socket on the pin sections disposed on the side of the top dead center, is used to intercept the rotation of the crankshaft. In this state, the connecting rod is joined by the aid of all of the pin sections of the crankshaft.
Japanese Laid-Open Patent Publication No. 5-318241 discloses a pitch change mechanism for a multi-spindle nut runner apparatus comprising a plurality of nut runner spindles incorporated into a sliding member. A driven member, which is provided on the sliding member, is engaged with a cam groove of a cam. Displacement of the cam causes the plurality of nut runner spindles to make mutual approach or separation by the aid of the driven member and the sliding member so that a plurality of bolts or nuts are simultaneously tightened.
Japanese Laid-Open Utility Model Publication No. 4-136630 discloses a nut runner pitch-adjusting mechanism for nut runner holders. The nut runner pitch-adjusting mechanism is arranged as follows. That is, guide blocks are provided on a pair of guide rails which make intersection at a center of the nut runner holders. The pitch of the nut runners is changed by moving the guide blocks along the guide rails.
However, in the case of the conventional technique described above, for example, when the type of the crankshaft is changed from a crankshaft of the L-type engine to a crankshaft of the V-type engine, it is necessary to change not only the spacing distance of the attachment members for attaching the connecting rod to the crankshaft, but also the attachment angle and the spacing distance between the connecting rod and another adjacent connecting rod. Further, it is necessary to exchange the tightening apparatus corresponding to the type of each of the engines. Therefore, problems arise in that the exchange operation is complicated, the time required for the operation is prolonged, and the production cost becomes expensive.